Organic light emitting devices are self-luminous device, have a wide viewing angle, excellent contrast, fast response time, high brightness, and excellent driving voltage and response rate characteristics, and can realize a multicolor display.
Normal organic light emitting devices may include an anode, a cathode, and an organic layer interposed between the anode and the cathode. The organic layer may include an electron injection layer, a hole transport layer, a light emitting layer, an electron transport layer, cathode, etc. When a voltage is applied between the anode and the cathode, holes injected from the anode is transferred to the light emitting layer via the hole transport layer, and electrons injected from the cathode is transferred to the light emitting layer via the electron transport layer. Carriers, such as the electrons and the holes, recombine in the light emitting layer to generate excitons, which generate light while being changed from an excited state to a ground state.
In order to increase efficiency and life of the device, the organic light emitting devices have been developed in such a way to increase an auxiliary layer (or a buffer layer), such as a hole injection layer, a hole transport layer, and an electron transport layer. Accordingly, costs for materials and processes for manufacturing the device have gradually increased, and how to solve the problem has become a major issue in the organic light emitting device.
When the auxiliary layer of the organic light emitting device is formed in a thin film or removed, the distance between the light emitting layer and the electrode (for example, the anode or the cathode) may be reduced, resulting in occurrence of an exciton quenching phenomenon in the light emitting layer. That is, the auxiliary layer, such as the hole injection layer, the hole transport layer, and the electron transport layer, may function to prevent the exciton quenching phenomenon in the light emitting layer.
Accordingly, in order to manufacture a high quality organic light emitting device, it is important to minimize the exciton quenching phenomenon with simplifying the structure of device by removing the auxiliary layer, such as the hole injection layer, the hole transport layer, and the electron transport layer.